1. Field of the Invention
The present invention relates to making insulated glass units used in residential, architectural and vehicle applications. More specifically, it refers to the manufacture of insulated glass (IG) units having coatings applied exhibiting solar control, low-E, and impact resistant properties.
2. Description of the Prior Art
Insulated glass windows or door units have been known for many years to reduce the heat transfer between the interior house and the environment. To further improve the insulating properties, the art taught making solar control coated and low-emissivity (low-E) coated glass or film.
Solar control is a term describing the property of regulating the amount of solar heat energy, which is allowed to pass through a glass article into an enclosed space such as a building or an automobile interior. Low emissivity is a term describing the property of an article's surface wherein the absorption and emission of mid-range infrared radiation is suppressed, making the surface a mid-range infrared reflector and thereby reducing heat flux through the article by attenuating the radiant component of heat transfer to and from the low emissivity surface. By suppressing solar heat gain, building and automobile interiors are kept cooler, allowing a reduction in air conditioning requirements and costs. Efficient low emissivity coatings improve comfort during both summer and winter by increasing the thermal insulating performance of a window.
Two typical coating methods to make solar control and low-E coatings are “in-line” and “off-line” coatings. The in-line method uses a chemical deposition method involving doping with different chemicals to make an infrared absorbing layer and low-E layer as described in U.S. Pat. Nos. 5,750,265, 5,897,957, and 6,218,018. The off-line method uses sputtering deposition to make both coatings.
Impact resistant glass is described in detail in the Florida Building Code. Basically, it specifies a testing protocol for a window glass to withstand up to nine pounds of force from a 2×4 board shot at the glass up to 50 feet/second. Withstanding both shots with one in the center and one in the corner without penetration, is considered as a pass.
U.S. Pat. Nos. 4,799,745 and 5,071,206 describe a multi-layered sputtering polyethyleneterephthalate (PET) window film construction, which gives both solar control and low-E properties. The coating-contains silver metal layers and indium-tin oxide layers in an alternate construction. The film has a high visible light transmission, above 70%, and a low visible light reflection, about 8%. The total solar heat rejection is about 56%. The color of the coating is light green. It has a very good solar control and low-E performances. However, corrosion is a major concern. To make an IG unit, it needs edge deletion and filling with inert gas in the IG unit to prevent the coating from corroding. The multi-layered coating has to be exposed within the IG unit to achieve both low-E and solar control functions. As a result, the manufacturing process becomes expensive.
U.S. Pat. Nos. 5,332,888 and 6,558,800 disclose a multi-layered sputtering window glass construction (off-line method), which also achieves both solar control and low-E properties. The former patent contains a silver metal layer sandwiched by zinc oxide layers and the latter contains a silver metal layer sandwiched by nickel chrome and silica nitrite layers. Similar to sputtered PET film, they also face corrosion, chemical resistant and scratch resistant concerns.
U.S. Pat. No. 6,546,692 assigned to Film Technologies International, Inc. discloses a method of laminating a safety film on the inside surfaces in an IG unit to build an impact resistant window. The safety feature is very important for window glass to withstand hurricane, earthquake, and terrorism. However, the low-E property would be destroyed or significantly weakened once a safety film is laminated over the low-E coating surface.
Besides solar control, low-E, and impact resistance, other desirable properties include an economic process, durability, maintenance, light transmission, visibility, color, clarity and reflection. These are important features during a window manufacturing process.
To meet the Government (Department of Energy) Energy Star Qualification Criteria for Windows, Doors and Skylights and Florida Building Code for impact resistant windows, a new window/door design is required for the window/door industry.